The present invention relates to a traveling assembly for vehicles, which assembly is intended to be able to travel after a consequent and unexpected loss of pressure of the tire of the assembly, the tire being more particularly either a tubeless tire of the heavy-vehicle type or a tire for a passenger car, the H/B aspect ratio generally being at most equal to 0.8 in both cases. The assembly, apart from the tire and the mounting rim, comprises a supporting means for the tread of the tire when there is a loss of pressure. The invention also relates to the supporting means.
Although tires having a radial carcass reinforcement and crown reinforcement are less and less subject to slow or rapid deflation, and to becoming flat, whatever the cause(s) of said flat, the fact remains that there are still accidents and that a loss of pressure can result in many disadvantages, depending on the position of the tire on the vehicle and the rapidity of deflation. The most widespread disadvantages remain the loss of control of the vehicle, the replacement of the tire under conditions which are not always the most suitable, and practically in all cases deterioration of the properties of the tire, which deterioration may be partial or total.
Many proposals have been made to obtain a traveling assembly which is capable of traveling despite the loss of pressure of the tire of the assembly, and it would be tedious to list all the patent applications and/or patents relating to solutions for the problem. There will be discussed only the conventional, universally known means for solving said problem.
A supporting ring for a tread, which may be of one piece or of several pieces, either formed of a single material, generally a metallic material, or formed of two materials, metal and rubber, possibly being of different geometrical shapes, is inserted into the tire cavity such that the inner wall of the crown of the tire can make contact with the radially upper wall of the supporting ring. One such example of a supporting ring is described in U.S. Pat. No. 5,450,887.
It is also possible to use rings made of foam or cellular material, which under the normal pressure conditions of the tire occupies a certain volume of the tire cavity and which dilates when the internal pressure decreases, until the total volume of said cavity is occupied.
Another solution consists in inserting into the inner cavity of the tire a second, so-called inner tire, having a structure comparable to that of the first tire. The inner tire, which is of smaller dimensions, is then inflated to a pressure greater than the pressure existing in the inner cavity of the first tire, or at least in the free space between the inner wall of the outer tire and the outer wall of the inner tire, such that the outer tire comes to bear on the inner tire in the event of deflation of the outer tire. Japanese application 74/111,303 of Oct. 23, 1974 describes an inner tire of this type.
Whatever the solution adopted, it has disadvantages: a tread supporting ring made of metal or of two materials is costly, heavy and difficult to manipulate despite its lack of height, compared with that of the tire into which it is inserted. It does not enable the tire of the assembly to travel, after deflation, with a deflection compatible with good resistance to internal deterioration of the tire. The same is true of inner tires, which, although less heavy, are just as difficult to handle individually. As for rings of foam or cellular material, they cannot be used for all dimensions of tire because of the high cost of the traveling assembly, while not having any particular advantage from the point of view of assembly and manipulation compared with the use of an inner tire. Quite the contrary, the increase in the internal heating of the tire due to the presence of an inner foam body practically prevents use thereof in a tire of large dimensions.